Splunk DMS(6.4 and lower) or Monitoring Console(6.5) report the number of physical CPU cores, not virtual CPU cores.
Your AWS "C4.2xlarge" may have 8 virtual CPU cores, not 8 physical CPU cores.
Splunk may recognize your all cores. There is nothing to worry about.
I'd like to share my findings.
AWS "C4.2 xlarge" uses hyper-threading enabled CPU, AWS says in this https://aws.amazon.com/jp/ec2/instance-types/.
Please try to find "ハイパースレッド" word in that URL.
You may find "各 vCPU は、M4、M3、C4、C3、R3、HS1、G2、I2、D2 の Intel Xeon コアのハイパースレッドです。".
It means that your "C4.2xlarge" has 8 virtual Cores, not 8 physical Cores.
And, could you try to search the following on your Splunk.
index=_internal cores
You may find the following Splunk internal events, which explain the number of virtual and physical cores your Splunk recognizes.
12-14-2016 19:54:32.770 + 0900 INFO loader – Detected 4 (virtural) CPUs, 2 CPU cores, and 4022MB RAM
### This event is my Splunk internal log.
My Splunk Monitoring Console says 2 CPU cores, not 4 cores.
I hope this information may help you.
By the way, Splunk Ver 4.2.2 is old and doesn't have DMC. I think you may use later version of Splunk.
Thank you.
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